Thickness dependence of high-k materials on the characteristics of MAHONOS structured charge trap flash memory

The electrical characteristics of tunnel barrier engineered charge trap flash (TBE-CTF) memory of MAHONOS (Metal/Al2O3/HfO2/SiO2/Si3N4/SiO2/Si) structure were investigated. The stack of SiO2/Si3N4/SiO2 films were used as engineered tunnel barrier, HfO2 and Al2O3 films were used as charge trap layer and blocking oxide layer, respectively. For comparison, the electrical characteristics of MONOS (Metal/SiO2/Si3N4/SiO2/Si), MONONOS (Metal/SiO2/Si3N4/SiO2/Si3N4/SiO2/Si), and MAHOS (Metal/Al2O3/HfO2/SiO2/Si) were also evaluated. The energy band diagram was designed by using the quantum-mechanical tunnel model (QM) and then the CTF memory devices were fabricated. As a result, the optimized thickness combination of MAHONOS structure was confirmed. The tunnel barrier engineered MAHONOS CTF memory showed a considerable enhancement of program/erase (P/E) speeds, retention time and endurance characteristics.